In the conventional scroll compressor of this kind, to reduce leakage loss in a compressed chamber and to obtain high efficiency, an orbiting scroll is brought into contact and slide with a fixed scroll, and the compressed chamber is sealed in many cases. FIG. 5 shows an example of a conventional structure described in patent document 1 (Japanese Patent Application Laid-open No. 2001-280252). That is, in the conventional scroll compressor, a back pressure chamber 12 is provided on a surface on the opposite side (back surface) from an orbiting scroll wrap surface of an orbiting scroll 5. The back pressure chamber 12 is divided into an inner region 12a and an outer region 12b by an annular seal 11. Lubricant oil in a discharge pressure state is supplied to the inner region 12a of the annular seal 11, a portion of this lubricant oil is supplied to the outer region 12b through a narrowed portion 13, and the lubricant oil of the outer region 12b is supplied to a suction space 9. With this configuration, the outer region 12b is set to an intermediate pressure Pm between a suction pressure Ps and a discharge pressure Pd, thrust force is applied to a back surface of the orbiting scroll 5, thereby allowing the orbiting scroll 5 to come into contact and slide with a fixed scroll 4.
According to the above structure, when the scroll compressor is started, lubricant oil is first supplied to the inner space 12a of the annular seal 11 and then, is supplied to the outer space 12b, but lubricant oil is not supplied to the suction space 9 formed by both the scroll until the pressure in the outer space 12b becomes equal to the set intermediate pressure Pm (=Ps+ΔP). When lubricant oil is not supplied to the suction space 9 at the time of starting of the scroll compressor, if a large amount of refrigerant liquid is returned to the suction space 9 from the refrigeration cycle together with refrigerant gas, there is a problem that lubricant oil remaining on a sliding surface is washed away and as a result, and the fixed scroll 4 or the orbiting scroll 5 is damaged and seized up.
Especially when the refrigerant has high pressure like carbon dioxide (CO2), an absolute value of thrust force which pushes the orbiting scroll 5 against the fixed scroll 4 becomes high, and an absolute value of a set back pressure ΔP (=Pm−Ps) also becomes high. Therefore, a duration of lubrication delay becomes longer as compared with refrigerant R410A and thus, there is a problem that the fixed scroll 4 and orbiting scroll 5 are more prone to be seized up.
Hence, it is an object of the present invention to provide a reliable scroll compressor capable of preventing lubrication delay at the time of start of the scroll compressor.